Educated at the University of Cambridge, in 1958 he became director of the Applied Psychology Research Unit, set up by the UK Medical Research Council in 1944 to focus on Frederick Bartlett's work. Although most of the work at the APRU was directed at practical issues of the military or private industry, Broadbent became well known for his theoretical work. His theories of selective attention and short-term memory were developed as digital computers were becoming available to the academic community, and were among the first to use computer analogies to make serious contributions to the analysis of human cognition. These theories were combined to form what became known as the "single channel hypothesis." Broadbent's filter model of attention proposed that the physical characteristics (e.g., pitch, loudness) of an auditory message were used to focus attention to only a single message. Broadbent's filter model is referred to as an Early Selection Model because irrelevant messages are filtered out BEFORE the stimulus information is processed for meaning. These and other theories were brought together in his 1958 book Perception and Communication, which remains one of the classic texts of cognitive psychology.[4] In 1974 Broadbent became a fellow of Wolfson College, Oxford and returned to applied science; along with his colleague Dianne Berry, he developed new ideas about implicit learning from consideration of human performance in complex industrial processes.

Broadbent's Filter Model of Attention proposes the existence of a theoretical filter device, located between the incoming sensory register, and the short-term memory storage. His theory is based on the multi-storage paradigm of William James (1890) and the more recent 'multi-store' memory model by Atkinson & Shiffrin in 1968. This filter functions together with a buffer, and enables the subject to handle two kinds of stimuli presented at the same time. One of the inputs is allowed through the filter, while the other waits in the buffer for later processing. The filter prevents the overloading of the limited-capacity mechanism located beyond the filter, which is the short-term memory.[4] Broadbent came up with this theory based on data from an experiment: three pairs of different digits are presented simultaneously, one set of three digits in one ear, and another set of three digits in the other. Most participants recalled the digits ear by ear, rather than pair by pair. Thus, if 496 were presented to one ear and 852 to the other, the recall would be 496852 rather than 489562.

The theory has difficulties explaining the famous cocktail party effect, proposed by British scientist Colin Cherry, which tries to explain how we are able to focus our attention towards the stimuli we find most interesting.[5]